Figure 1. Solvent protection ratios for backbone amide protons as determined by quenched H/D exchange monitored by NMR spectroscopy.

Protection is defined as the ratio of the observed signal intensity after a 24 h pre-incubation period in D₂O to the signal intensity in a completely protonated reference sample. Protection in the reference sample is defined as 100%. Circles correspond to residues with 0% protection and crosses to residues where exchange was too fast for detection. Pale grey bars indicate overlapping residues with ambiguously assigned protection ratios. Error bars indicate the experimental uncertainty given by the measurements. (A) Aβ^40Arc fibrils, (B) Aβ^40WT fibrils, and (C) Aβ^40Arc seeded with Aβ^40WT fibrils.